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Validity of the Cloud Model of the Interstellar Medium

Published online by Cambridge University Press:  03 August 2017

Bertram Donn
Bertram Donn*
Affiliation:
Department of Physics, Wayne State University, Detroit, Michigan

Extract

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Because of the extreme irregularity in distribution of interstellar matter, some idealized model must be adopted in discussing the interstellar medium. Three simple models have been considered. The original one, long-since discarded, was a uniform distribution. This has been largely replaced by the random cloud picture in which space is visualized as filled with isolated clouds, 5–10 per kpc, about 10 pc in diameter, the array having an exponential velocity distribution with a mean of about 8 km/sec. Lastly, there is a turbulent or a random density fluctuation model.

Although the random cloud hypothesis has received most attenuation from astronomers, it has been well recognized that it is an over simplified model and should be used with some caution. This point of view has been clearly stated by many workers in this field, as the following statements by Oort and by Minkowski, respectively, demonstrate.

Type
Part I: Empirical Studies of Velocity Fields in, and Related Structure of, the Interstellar Medium
Information
Symposium - International Astronomical Union , Volume 8: Cosmical Gas Dynamics , July 1958 , pp. 940 - 942
Copyright
Copyright © American Physical Society 1958 

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